Ijen Crater (Kawah Ijen)

Ijen is a volcanic complex in eastern Java. The Smithsonian Global Volcanism Program describes its crater lake as a nearly kilometre-wide body of turquoise water, among the most acidic natural lakes known, holding an estimated 30 million cubic metres. The volcano's last recorded eruption was in 1999, but it remains active, and authorities raise and lower its alert level as conditions change; in July 2024 the exclusion zone was temporarily widened to 1.5 km from the crater before activity eased in August.

Sulphur has long been extracted from fumaroles at the lake's edge, where pipes channel the gas so that it condenses into sulphur. Miners break the cooled sulphur into pieces and carry loads reported at 75 to 90 kg out of the crater. The area, part of the Ijen Geopark, is managed for tourism by East Java's Natural Resources Conservation Agency (BBKSDA Jawa Timur) as the Kawah Ijen Nature Recreation Park.

The miners of Ijen come mainly from villages around Banyuwangi and Bondowoso, and their work is physically punishing and exposes them to harmful fumes. Many also earn extra income from tourism, by guiding or carrying visitors on wheeled carts, and some sell small sulphur souvenirs. Around the volcano, the highlands of Bondowoso and Banyuwangi are known for coffee plantations and farming villages, and Banyuwangi has its own distinct Osing culture.